Circuit breaker



CIRCUIT BREAKER Filed April 5, 1937 2 Sheets-Sheet l /N VENTO/e Olav456175 Feb. 11, 1941. o, MASENG 2,231,081

CIRCUIT BREAKER Filed April 5, 19,37 2 Shorty-Sheet 2 fren/f@ O 55-9 O l1515 4T/f :L 54* .54 G Eff@ "I C@ C@ @o ff m62 fg-f E- E. TQ @D w l l1 LPanarea Feb. 11, 1941 UNITED STATES PATENT OFFICE D Company, Detroit,

Michigan Mich., a corporation of Application April s, 1937, serial No.134,979

llOlaims.

This invention relates to thermostatic current responsive elements Aforautomatic circuit controlling devices and has for its object theprovision of a thermostatic means responsive to circuit current whichshall have increased sensitivity and be less affected by changesinambient temperature.

`Another object of this invention is to provide a current responsivethermostatic means for elecl tric circuit controlling devices with asurface on its heat dissipating portions which shall reduce the emissionof heat from these portions.

Another object of' the invention is to provide current responsivethermostatic means for eleci tric circuit controlling devices whichshall be more uniform in their operation.

Other objects and features of this invention will be readily apparent tothose skilled in the art from the following specification and v appendeddrawings illustrating certain preferred embodiments of the invention inwhich:

Figure i is a partial front elevational view of an automatic electriccircuit breaker utilizing a current traversed bimetallie elementaccording to ,26 the present invention and in which portions are cutaway to show internal parts.

Figure 2 is a vertical sectional view taken on the line II-II of Figurei.

Figure 3 is a detailed sectional view of the bimetallic element taken onthe line IIIj--m of Figure 2.

' Figure 4 is a view similar to Figure 3 but showing another embodimentof the invention.

Figure 5 is a front elevational view with parts 38 vcut away of a motorstarting switch utilizing the solder pot type current responsiveoverload means.

Figure 6 is an enlarged detailed view of one of the solder pot typethermostatic means' used in the switch of Figure 5. I

Figure 'I is a sectional view on the line VII--VII of Figure 6.

Figure 8 is a view similar to` Figure 7 showing another embodiment ofthe invention.

Figures 1 to 4 inclusive are directed to the invention as applied to acurrent traversed bimetallic4 member used in an automatic electriccircuit breaker. As disclosed, this circuit breaker is of the typedisclosed and claimed in the copending applications of John G. Jackson,Serial No. 36,247, filed August 15, 1935, Serial No. 72,035, filed April1, 1936, Serial No. 77,519, filed May 2, 1936, all ventitled Circuitbreakers, and in the divisions and continuations of these applications.The circuit breaker embodies a metallic mounting (ci. zoo-11a) plate Iwhich may be the back wall of an outer enclosing box against which ismounted a cupshaped insulating base 2. Generally centrally of this baseis mounted a stationary contact plate 3 as by means of a stud 4 andcarrying stationary '5 contacts adapted to cooperate with movablecontacts 5 on the ends of contact blades l. At end ledges at the ends ofthe base are rigidly supported connectors l as by means of spun overportions of metallic inserts 8 which also receive `l0 terminal studs 3.To the interior end of each of the connectors I is rigidly secured oneend of a bimetallic member I I as by means of an adjusting meansdesignated generally at I2. The free end of the bimetallic member I Iand the contact blade l5 8 are electrically connected by means of aflexible lead Il. A compression spring I4 biases the blade against thestationary contact and the free end of the birnetallic member II. AU-shaped member I5 having legs of dissimilar length is 20 guided byformations in the base for rectilinear movement at right angles thereof.The longer leg of the member I5 is slottedto receive the blade 6 and theblade at its top edge is provided with a notch I6 received within thetop edge of 25 the slot. A second notch I'I is provided in the frontedge of the blade and is adapted to engage a shorter leg of the memberI5 to serve as a stop for the blade upon rotation as hereinafterdescribed. An operating handle I8 pivotally mount- 30 ed on a shaft I9has an interior cam surface 4which effects rectilinear movement of themember I5, which cam surface includes a fiat stable portion 2i and aresetting tip 22.

The blade shown at the top of Figure 2 is in the 35 normal on position.'To move the parts to the manual off position the handle is rotatedcounterclockwise until the flat surface 2| engages the top surface ofthe member I5 which produces a stable position in which the member I 5has been 40 moved toward the bottom of the base and has separated themovable contact at the end of the associated blade l from itscooperating stationary contact. The movable contact and blade are thenin the position shown partially adjacent the 45 bottom of Figure 2. Inautomatic release upon the occurrence of an overload through the circuitbreaker mechanism shown at the top of Figure 2 its bimetal will becomeheated and will flex upwardly until it releases the latched end oi.'con'- 50 tact blade 6 whereupon this blade rotates in a counterclockwisedirection about the engagement of the notch I6 with the member I5 andunder the bias of spring I4 into a contacts disengaged position, thusinterrupting the circuit through the breaker mechanism. To reset theparts after an automatic release the handle is rotated past theoiTposition until the latching tip 22 is on the top surface of themember l5 in which position the contact blade 6 will have engaged thebottom of the arc chamber and moved back into position to engage thebimetallc latch Il. If this latch has cooled suiiiciently to assume itsnormal position, release of the handle will then place the parts in thenormal off position whereupon clockwise rotation of the handle willagain permit the parts to assume the position shown in Figure 2, theclosed circuit position.

rllhe bimetal il embodying the features of the present invention isshown in greatly thickened scale in order to denote the layers thereof.These are more fully shown in Figure 3 in which again the proportion ofthe parts has not been retained. The bimetal is formed of two metals 23and 2l having dissimilar thermal coefficients of eXpansion which areintegrally bonded together to form a single strip which will bend inwell-known manner upon changes in temperature. About this bimetallicstrip is plated or otherwise disposed a surface coating 25 which willserve to decrease the transmission of heat to or from the birnetal.Figure 4 is similar to Figure 3 but here the bimetal formed of thestrips 23 and 24 is provided with a double coating 26 and 2l as has beenfound desirable and as will be more fully explained hereinafter.

Figures 5 to 8 inclusive illustrate the features of applicants inventionapplied to a motor control switch using a solder pot type overloadrelease. This is illustrated in connection with the switch which is morefully disclosed in Patent No. 1,912,109 granted May 30, 1933 to H. L VanValkenburg, et al., and reference is made thereto for the parts notshown herein. This includes an enclosure 5i within which is mounted abase 52 supporting stationary contacts 53 and movable contacts 54 whichare carried on an insulating block 55 reciprocable at right angles tothe base 52.- As more fully explained in the patent disclosure, means isprovided for holding the contacts engaged and for releasing the holdingthe block 55 in response to melting of the holding metal in the overloadrelays indicated generally at 56. The overload relays 56 are moreparticularly shown in Figures 6 and '7 and embody end terminals 51between which extend a heater strap 58 insulated at the front by meansof a plurality of thin mica strips 59. At the back of the heater strap58 are placed one or more thin sheets of mica insulation SI whose numberdetermines the heat lag to the holding metal alloy to be described.Against the mica plate 6I is disposed a metallic block 62 having acylindrical chamber 63 therein in which is disposed a shaft 64 and analloy metal E5 surrounding and holding the shaft 64. At the end of theshaft 64 is disposed a ratchet Wheel 66. A clamp 61 is disposed aboutthe unit and serves to hold the metal block 62 in heating conductingrelation with `the heater 58. The metallic alloy 65 is chosen to have afusion point at a certain desired temperature and its softening willpermit ratchet wheel 66 to yturn and this operates as described in thepreviously cited patent to initiate operation of the switching parts toopen the circuit therethrough. The metallic block B2 and other heatdissipating metallic portions are here provided with a coating 68serving to reduce the emission or transmission of heat from thethermostatically sensitive parts. The solder pot overload relay shown inFigure 8 is the duplicate of that shown in Figure 7 with the exceptionthat here two coatings 69 and 1I are shown for the heat dissipatingparts.

While applicants inventive concept iinds its greatest advantages inbimetallic current traversed members it is also advantageously used inthe solder pot type relay of Figures 5 to 8 inclusive and applicantsinvention is to be broadly construed asapplying to any currentresponsive thermostatic member wherein there are heat absorbing or heatdissipating surfaces.

According t`o applicants invention the surface on the thermostaticelement is preferably an electro-plated coating known as bright chromiumwhich consists of an electro-plated coating of nickel directly on theelement followed by an electro-plated coating of chromium on top of thenickel coating. B`oth o'fthese coatings are preferablyl made as thin asis consistent with good coating practice. This double coating appears togive the most advantageous results and as it is also relativelypermanent and non-tarnishable is selected as the preferred coating.However, it has also been determined tha-t a coating of silver appearsto give beneficial results but due to its high conductivity is apt todisturb the resistance of the bimetallic element of the type of Figures14 to 4 inclusive and it also tarnishes easily which results in adecrease in its effectiveness. A coating of nickel alone has also beenfound to have some advantageous effects but these are considerably lessthan the chromium on nickel coating previously discussed. A coating ofzinc also appeared to be beneficial but this is undesirable due to itsrelatively high conductivity when applied as a coating and also to itstarnishabilty. A coating of whi-te paint was also found to havebeneficial effects but is undesirable as it darkens and/or chars quicklyand is apt to flake due to mechanical stress. Applicants invention is tobe construed as covering any surface on the thermal element whichdecreases the emission or transmission of heat and while the chromium onnickel coating is preferred because of its other properties it isobvious that many other materials including those mentioned above can beused with varying results to produce the desired effect.

Tests of the thermal elements provided with coatings according to thepresent invention indicate that in the bimetal there is an increaseddeflection due to an increased internal temperature which is caused bythe heat retention since radiation and other heat losses from thebimetal are greatly reduced by the coating. This results in either theuse of a heavier bimetal to produce the same deflection or in the use ofgreater mechanical latching overlap or in the use of a lesser trippingcurrent. One very important result which is perhapsmore important incase of the bimetallic strip although also present in the solder pottype unit is the lessened effect upon the performance Yof changes in thetemperature surrounding theelement. As ordinarily the heat emitted fromthe element will vary with the temperature difference to the surroundingatmosphere it is apparent that if this emission is greatly cut down thatthe temperature of the element will obviously be less affected bychanges in this difference in temperature. Hence the element is lessaffected by change in the surrounding temperature. Furthermore, in agiven bimetallic strip having a given resistance the Coating accordingto the present invention provides for a higher internal temperaturewhich means that the bimetal for the same current will be calibrated asto latching overlap at a higher temperature and this will result in thebimetal being less affected by ambient temperatures on the ou-tside ofits enclosure where there is heat dissipation due to conduction throughthe connecter to the external terminal and to the circuit wiring. If thebimetal is operating at a higher ltemperature it is obvious that it willbe less affected by changes in the ambient temperature about theconnecter and the temperature of the circuit wiring to which itdissipates heat. In `the case of the solder pot relay the coating,according to the present invention, permits the use of a heavier andlower resistance heating strip to produce the same temperature for thesame overload current in the fusible holding metal and also makes theunit less responsive to changes in surrounding temperature. In the caseof the bimetallic strips it is also noticed that the coating appears toreduce variations between individual bimetals which may have been causedby surface variations in the individual bimetals. It also permits anincreased standardization by permitting the use of the same crosssectional and resistance bimetals over a wide current range dependingupon whether they are plated or not. Furthermore, particularly indevices where the thermostatic units are used in close proximity toother thermostatic units a benecial effect is noted inasmuch as, due tothe decreased emission of heat from the units, the internal temperaturesof the devices will be lowered sinceA less heat is wasted to them by theunits; also should the internal temperature of the device be raised dueto the heat emitted from uncoated units or from any other source, thisincrease in temperature will have a reduced effect upon the units coatedin accordance with the present invention as has been explainedheretofore.

While certain preferred embodiments of the invention have beenspecifically disclosed, it is understood that .the invention is notlimited thereto as many variations will be readily apparent to thoseskilled in the art and the invention is to be given its broadestpossible interpretation. within the terms of the following claims.

What is claimed is:

l. In an automatically opening'circuit controlling device havingcooperating contacts and means for effecting separation of said contactsto open the circuit therethrough, thermostatic means for initiatingoperation of said first mentioned means in response to the heatgenerated by the passage of current through the device in excess of apredetermined value, and reflecting, heat retaining surfaces on heatdissipating portions of said thermostatic means.

2. In an automatically opening circuit controlling device, a stationarycontact, a contact cooperating therewith and movable to effect openingand closing of the circuit therethrough,

means biasing said movable contact to separated position to open thecircuit, thermostatically controlled means holding said contacts inengaged position against the force of said biasing means, thethermostatic means operating to effect the release of said movablecontact for movement thereof to separated position under the action ofits biasing means in response to the heat generated by the passage ofcurrent through the device in excess of a predetermined value, and

surfaces on said thermostatic means inhibiting the normal heat wastetherefrom.

3. In an automatically opening circuit controlling device havingcooperating contacts and means for effecting separation of said contactsto open `the circuit therethrough, thermostatic means for initiatingoperation of said first mentioned means in response to the heatgenerated by the passage of current through the device in excess of apredetermined value, said thermostatic means being provided with acoating decreasing the normal heat emission from its surfaces.

4. In an automatically opening circuit controlling device, a stationarycontact, a contact cooperating therewith and movable to effect `openingand closing of the circuit therethrough,

means biasing said movable contact to separated position to open thecircuit, thermostatically controlled means holding said contacts inengaged position against the force of said biasing means, thethermostatic means operating to effect the release of said movablecontact for miovement -thereof to separated position under the action ofits bi-asing means in response to the heat generated by the passage ofcurrent through the device in excess of a predetermined value, saidthermostatic means being provided with a bright, reflecting surfacecoating which reduces its sensitivity to changes in surroundingtemperatures.

5. In an automatically opening circuit controlling device havingcooperating contacts and means for effecting separation of said contactsto open the circuit therethrough, thermostatic X means for initiatingopenation of said iirst mentioned means in response to the heatgenerated by the passage of current through the device in excess of apredetermined value, said thermostatic means being provided with a thincoating formed of layers of chromium on nickel.

6. In an automatically opening circuit controlling device havingcooperating swiitching con-l tacts, of which one is stationary and theother is movable to and from engagement therewith to effect opening andclosing of the circuit through the device and means for biasing saidmovable contact for movement to a position separated from saidstationary contact, a bimetallic element for effecting release of saidmovable contact for movement to separated position under the action ofits biasing means, said bimetallic element being connected in seriescircuit with said contacts so as to be traversed by the current flowingtherethrough and operating to effect release of said movable contact inresponse to the heat generated in itself by the passage of current inexcess of a predetermined value, and means for increasing the internaloperating temperature of said bimetallic element comprising a surfacecoating reducing the heat emission therefrom.

7. In an automatically opening circuit controlling device havingcooperaltlng switching contacts, of which one is stationary and theother is movable to and from contact therewith to effect opening andclosing of the circuit through the device and means for biasing saidmovable contact for movement to a position separated from saidstationary contact, a bimetallic element for effecting release of 'saidmovable contact for movement to separated position under the action ofits biasing means, said bimetallic element being connected in seriescircuit with said contacts so as to be traversed by the current flowingtherethrough and operating to effect release of said movable contact inresponse-to the heat generated in itself by the passage of current inexcess of a predetermined value, and a bright, metallic, reflectingcoating on said element substantially reducing the heat emissiontherefrom.

8. In an automatically opening circuit controlling device havingcooperating switch contacts and means for effecting separation of saidcontacts to open fthe circuit through the device, a bimetallic elementconnected in series circuit With said contacts so as to be traversed bythe current passing therethrough and operating to effect initiation ofsaid means in response to the heat generated in itself by the passage ofcurrent in excess of a predetermined value, said bimetallic elementhaving a thin coating formed of electro-deposited layers of chromium onnickel. l

9. In an automatically opening circuit controlling device havingcooperating switching contacts and means for effecting separation ofsaid contacts fto open the circuit through the device, a. thermostaticunit for initiating operation of said means, said unit including aheater element connected in series circuit with said contacts so as tobe traversed by the current flowing therethrough, a fusible metal inheat conducting relation with said heater and an element normally heldimmovable by said metal when in a solid state but released for movementupon fusion of said metal, and means for increasing the temperature ofsaid fusible metal in response to a given circuit current through theheater element comprising a surface coating on said unit reducing theheat emission therefrom.

10. In an automatically opening circuit controlling device havingcooperating switching contacts and means for effecting separation ofsaid contacts rto open the circuit through the device, a thermostatic unit for initiating operation of said means, said unit including a heaterelement connected in series circuit with said contacts so as lto betraversed by the current flowing therethrough, a fusible metal in heatconducting relation with said heater and an element normally heldimmovable by said metal when in a solid state but released for movementupon fusion of said metal, and a. bright, metallic, reflecting coatingon heat dissipating portions of said unit substantially reducing theheat emission therefrom.

11. In an automatically opening circuit controlling device, a stationarycontact, a. contact cooperating therewith and movable to effect openingand closing of the circuit therethrough, means biasing said movablecontact to separated position to open the circuit, a thermostatic unitfor effecting release of said movable contact for movement to separatedposition under the action of its biasing means, said unit including aheater element connected in series circuit -with the contacts so as tobe traversed by

